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Thread: Rigid Copper for A/C LineSet

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    Network Engineer rmelo99's Avatar
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    Default Rigid Copper for A/C LineSet

    Can rigid copper be used for A/C Lineset? If so what type.

    I know that soft copper pre-made linesets are typically used between the outdoor unit and air handler, but I would like to use rigid tubing to go from the 2nd floor air handler down and interior wall and run over to the outdoor unit in the basement.

    The air handler isn't installed, but I would like to get the pipe in the wall so I can close up the wall.

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    DIY Junior Member 41Fever's Avatar
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    The copper you would have to use is called ACR. Doubtful it can be had from any big box store. Also would want to use refrigeration fittings and joints need to be silver soldiered.

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    Plumber jimbo's Avatar
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    Most of the soft copper up to 1/2" OD sold at the hardware stores is ACR. 5/8 and 7/8 OD would be 1/2 and 3/4 type L.

    The important thing about ACR is that it is cleaned internally. If you wanted to use type L hard, some serious flushing would be required before connecting to the equipment. I would get input from a good HVAC contractor about the feasibity of this.

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    Network Engineer rmelo99's Avatar
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    Ok, so I pretty much figured I couldn't walk into the depot and pick the stuff up!

    So my line is 7/8 on the larger and can't remember on the smaller. How is 7/8 the same as 3/4? Is it I.D vs. O.D?

    Do they sell ACR in rigid lengths, and if so an HVAC supply house would sell them?

    Now another quick question to throw into the thread, can they be soldered like water pipe using silver solder, or do they have to be brazed?

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    Plumber Cass's Avatar
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    Brazing is the preferred way, less expensive and easier and you must have a nitrogen supply flowing through the pipe while doing it to prevent oxidation... anything foreign left in the line like flux or oxidation flakes can / may cause problems such as failure with the compressor.
    Last edited by Cass; 12-16-2008 at 06:52 AM.

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    Network Engineer rmelo99's Avatar
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    I did some research on the brazing with nitrogen. Looks like many out techs in the residential HVAC industry skip the "niitrogen" in the lines when brazing.

    What I read is that there is minimal brazing joints and minimal oxidation in the residential lines, and also if you use a filter before the air handler you sorta cover your self?

    I do not plan on doing many joints, if any. My plan to run the 2 lines down from the second floor to the basement so then the connections can be extended at the 2nd floor and basement to the units. I have the coiled lineset, but would rather not try and snake this down the wall cavity.

    The airhandler and outdoor units will be installed at the end of the season.

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    Engineer Furd's Avatar
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    If you really, REALLY want the hard temper tubing in the wall I strongly suggest that you get the installer you are going to use for the rest of the system to install the hard temper tubing. Otherwise, when it comes time for the rest of the installation you won't have any guarantee on the lines in the wall. Probably no guarantee on the system either.

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    Plumber jimbo's Avatar
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    ACR tubing is called out by OD. Type K,L,M hard tube ( what everyone calls copper pipe) is called out by trade size, which is approximate ID, and the OD is always EXACTLY 1/8 larger than the called out ID. For example, 1/2" tube is approximately 1/2" ID, but the exact ID varies with wall thickness, depending on whether it is K, L, or M. BUT IN ALL CASES, the OD is EXACTLY 5/8"

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    DIY Senior Member burleymike's Avatar
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    We use rigid tubing mostly in commercial jobs. For AC use I prefer soft copper because you don't have as many joints and you have less fittings. The more fittings the more resistance, and the greater chance of leaks/contamination.

    You must braze the joints and all manufacturers require you to do a dry nitrogen purge while brazing to prevent oxides from forming on the interior of the tubing. If you have a failure due to a bunch of oxide crud clogging the TXV they will not honor the warranty. A lot of guys don't do it and everything works fine but it is the proper way to do it.

    After you finish brazing all your joints you need to pull a deep vacuum (under 100 microns) to check for leaks and remove any moisture.

    Moisture is another problem using rigid lengths of lineset. It must be sealed and dehydrated from the factory or it will have crud and air which contains moisture inside.

    If your system will be using R410-A you will really have to be careful about moisture. The oil used with it loves moisture it soaks it up right from the air.

    I recommend you use soft copper, don't remove the rubber plugs just run the lineset and then hire an HVACR tech to braze the joints and charge the system. That way you don't have to spend thousands on tools you will use once. You will also know it is done right for the warranty sake.

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    Network Engineer rmelo99's Avatar
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    Ok, so I guess my plan to go rigid isn't getting the support I needed/wanted from you guys :-(. So I guess I'll take the advice given and use the coiled stuff!

    That being said I now need to snake this "semi-rigid" tubing that is all coiled up down a "straight" wall cavity. Any tips there?

    I have a 50' lineset already purchased I think it's 7/8" and 3/8" already insulated on the larger pipe.

    Thanks
    Rem

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    Retired Defense Industry Engineer jadnashua's Avatar
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    Can you fish a rope through that passage? Tie one end to it, and while someone is pulling, carefully uncoil the roll of the pipe.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    Network Engineer rmelo99's Avatar
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    Oh,the passage is wide open, I have the entire 2x4x14" wall cavity to run the line through.

    I just forsee this being a bit tricky, it's not like pulling romex or anything.

  13. #13
    Moderator & Master Plumber hj's Avatar
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    Default tubing

    I think you may wish to pull the copper UP from the basement so the rest of the coil can be extended to the unit.

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    Retired Defense Industry Engineer jadnashua's Avatar
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    With two people, one being careful to unroll and the other guiding it, you should be able to avoid kinks and guide it up (or down) the channel.
    Jim DeBruycker
    Important note - I'm not a pro
    Retired Defense Industry Engineer; Schluter 2.5-day Workshop Completed 2013, 2014

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    DIY Senior Member burleymike's Avatar
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    The hardest part is not tearing the insulation off the suction line when going through floor/ceiling penetrations. Second hard part is not to kink the suction line. 7/8 is a pain not to kink, just be gentle and take your time.

    You might need a tubing bender if you are not expierenced with the larger sizes of soft copper.

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